In the course of development of pollution-reducing engine systems for motor vehicles and for other power requirements, various systems have been proposed for driving the engines by the use of compressed air acting on hydraulic fluid. The compressed air is supplied from a readily rechargeable pressure tank and is applied to the working hydraulic fluid, which in turn is supplied to the engine cylinders through suitably timed admission valves to provide power strokes of the pistons, and on the return strokes the exhaust hydraulic fluid is returned to its reservoir for recirculation. The admission of the working fluid to the cylinders is usually controlled by a camshaft having individual cams acting on linkage systems operating respective pressure fluid intake valves for the cylinders. In engines having groups of cylinders which are alternately acted on by the working fluid it is uneconomical to employ camshafts with individual cam elements and associated valve-operating linkage systems, and the engines of this type usually involve a large number of heavy moving parts subject to frequent maladjustment and operational failure, are relatively cumbersome and noisy, and are inefficient in the utilization of the pressurized working fluid. Also, in the case of air-actuated hydraulic engines of the dynamically balanced type it is desirable to employ a more reliable arrangement for the synchronization of the timing of the power strokes of symmetrically-arranged cylinder groups in order to maintain a proper dynamic balance. Also, it is desirable to employ a more efficient arrangement for applying the pressurizing air to the hydraulic fluid for minimizing the air-recharging requirements and for insuring smooth circulation of the working hydraulic fluid.
Further background will be given by examining the following prior U.S. Pats. which appear to represent the closest prior art relating to the present invention, found in the course of a preliminary search:
______________________________________ Murphy, 4,018,050 Beckett et al, 3,507,189 Brown, 3,765,180 Otto, 3,779,132 Shafer, 3,024,809 Shafer, 2,915,042 ______________________________________